1. Field of the Invention
The invention relates generally to the design of line stop discs used to close off the bores of pipes during repair.
2. Description of the Related Art
Line stop repairs are repairs made in pipelines that are active and under pressure. Line stop repairs use hot tapping to intervene in the pipeline. Hot tapping is done by first constructing a branch line which will redirect fluid flow around the portion of the pipeline that requires repair. Then the pipeline is cut into and the flowbore of the pipeline is plugged with a line stop to redirect the flow through the branch line. Thereafter, repairs are conducted. An example of a hot tapping operation is found in U.S. Pat. No. 8,286,655 issued to Farrelly.
In order to plug the pipeline, a line stop disc is inserted into the flowbore. The line stop disc is directly exposed to the piped fluid. Hot tapping is problematic in instances where the pipeline carries heated fluid under high pressure. Piped liquids can often be at temperatures of 400°-500° F. Steam or hot liquid quickly degrades a flexible line stop disc that is formed of elastomer and/or fabric. Thermoplastics can melt or otherwise fail. The use of an all metal disc is more expensive and has problems creating the sealing needed to close off the pipeline.